Field-sequential Color Liquid Crystal Display (FSC-LCD) devices have many advantages. A three-color (e.g., red, green and blue (R, G, B)) backlight source is driven to illuminate a whole panel in a particular timing in the display device. As a result, three colors of light, e.g., red, green and blue (R, G, B) light, are emitted sequentially from each pixel unit. The light is received by the eyes of a human and mixed through an afterimage effect, so that it appears that the pixel unit illuminates continuously in the eyes of the human. Compared with other existing LCD devices, the field-sequential LCD device does not need expensive color filters, thus cost is greatly reduced. Moreover, there is no need to divide the pixel unit into three or four pixel sub-units in the field-sequential LCD device, thus a higher resolution is achieved. The field-sequential LCD device does not need a color filter which strongly absorbs the light, therefore the utilization of the backlight and the brightness of the display can be greatly improved and power consumption can be reduced.
FIG. 1 is a structural diagram of a cross section of a field-sequential LCD pixel unit. The field-sequential LCD pixel unit of FIG. 1 includes: an upper substrate 10; a lower substrate 15; a liquid crystal layer 18 between the upper substrate 10 and the lower substrate 15; and a backlight source 19 having three colors of R, G, B which is located at a side of the lower substrate 15 opposite the upper substrate 10. A common electrode 12 is provided on the upper substrate 10, and a pixel electrode 16 is provided on the lower substrate 15. A black matrix 11 is formed in a partial region between the upper substrate 10 and the common electrode 12, and the black matrix 11 is used for shielding light from the region of the lower substrate 15 outside the region of the pixel electrode 16. A thin film transistor 17 is formed at a position on the lower substrate 15 corresponding to the black matrix 11 on the upper substrate 10. The thin film transistor 17 is electrically connected with the pixel electrode 16 and serves as a switching element of the pixel electrode 16.
FIG. 2 is a structural diagram of a field-sequential LCD panel. The LCD panel of FIG. 2 includes: a plurality of horizontal scan lines 22, with each scan line 22 being connected with gates of thin film transistors 23 of a whole row of pixel units 24; and a plurality of vertical data lines 21, with each data line 21 being connected with sources of thin film transistors 23 of a whole column of pixel units 24. A driving circuit sends triggering signals in sequence via the scan lines 22 so that the thin film transistors 23 of the pixel units 24 are turned on and the pixel units 24 receive image data sent from the data lines 21.
FIG. 3 is a timing diagram of a driving method of a field-sequential LCD panel. The driving method includes scanning, according to the corresponding R, G, and B light, all the thin film transistors with the scan lines. As a result of the scanning, image data sent from the corresponding data lines is received by the pixel electrode while the thin film transistor is turned on. The driving method also includes charging and discharging a capacitor in each pixel unit, so that liquid crystal molecules in a liquid crystal layer are rearranged, and making the pixel unit emit corresponding light by utilizing a backlight source. The period 34 to display light of one color includes: scanning time 31 to complete scanning all the thin-film transistors of the entire display panel, liquid crystal response time 32, and backlight irradiation time 33. To display an image frame, the field-sequential LCD device displays three colors in sequence, the thin film transistors are scanned three times, and the liquid crystal molecules in the liquid crystal layer are rearranged three times. Therefore, the actual light emitting time of the pixel unit is only a portion of the entire time.
For the field-sequential LCD panel or other LCD panels (such as TN-LCD, IPS-LCD, FFS-LCD and VA-LCD), when displaying a plurality of image frames, the grayscale of the same pixel will change. The smaller the change in the grayscale of the pixel, the longer the liquid crystal response time. The larger the change in the grayscale of the pixel, the shorter the liquid crystal response time. If the change in the grayscale of the pixel is very small (such as from grayscale 1 to grayscale 2), the liquid crystal response time of the pixel will be long. This is disadvantageous for the field-sequential LCD panel etc. which requires a high refresh rate and a short liquid crystal response time.